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| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 align="center">Header <boost/python/implicit.hpp></h2> |
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| <hr> |
| |
| <h2>Contents</h2> |
| |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a></dt> |
| |
| <dt><a href="#functions">Functions</a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#implicitly_convertible-spec">Function Template |
| <code>implicitly_convertible</code></a></dt> |
| </dl> |
| </dd> |
| |
| <dt><a href="#examples">Example</a></dt> |
| </dl> |
| <hr> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| <code>implicitly_convertible</code> allows Boost.Python to implicitly |
| take advantage of a C++ implicit or explicit conversion when matching |
| Python objects to C++ argument types. |
| |
| <h2><a name="functions"></a>Functions</h2> |
| |
| <h3><a name="implicitly_convertible-spec"></a>Function template |
| <code>implicitly_convertible</code></h3> |
| <pre> |
| template <class Source, class Target> |
| void implicitly_convertible(); |
| </pre> |
| |
| <table border="1" summary="implicitly_convertible template parameters"> |
| <caption> |
| <b><code>implicitly_convertible</code> template parameters</b><br> |
| </caption> |
| |
| <tr> |
| <th>Parameter</th> |
| |
| <th>Description</th> |
| </tr> |
| |
| <tr> |
| <td><code>Source</code></td> |
| |
| <td>The source type of the implicit conversion</td> |
| </tr> |
| |
| <tr> |
| <td><code>Target</code></td> |
| |
| <td>The target type of the implicit conversion</td> |
| </tr> |
| </table> |
| |
| <dl class="function-semantics"> |
| <dt><b>Requires:</b> The declaration <code>Target t(s);</code>, where |
| <code>s</code> is of type <code>Source</code>, is valid.</dt> |
| |
| <dt><b>Effects:</b> registers an rvalue <code>from_python</code> |
| converter to <code>Target</code> which can succeed for any |
| <code>PyObject* p</code> iff there exists any registered converter |
| which can produce <code>Source</code> rvalues</dt> |
| |
| <dt><b>Rationale:</b> C++ users expect to be able to take advantage of |
| the same sort of interoperability in Python as they do in C++.</dt> |
| </dl> |
| |
| <h2><a name="examples"></a>Example</h2> |
| |
| <h3>C++ module definition</h3> |
| <pre> |
| #include <boost/python/class.hpp> |
| #include <boost/python/implicit.hpp> |
| #include <boost/python/module.hpp> |
| |
| using namespace boost::python; |
| |
| struct X |
| { |
| X(int x) : v(x) {} |
| operator int() const { return v; } |
| int v; |
| }; |
| |
| int x_value(X const& x) |
| { |
| return x.v; |
| } |
| |
| X make_x(int n) { return X(n); } |
| |
| BOOST_PYTHON_MODULE(implicit_ext) |
| { |
| def("x_value", x_value); |
| def("make_x", make_x); |
| |
| class_<X>("X", |
| init<int>()) |
| ; |
| |
| implicitly_convertible<X,int>(); |
| implicitly_convertible<int,X>(); |
| } |
| </pre> |
| |
| <h3>Python code</h3> |
| <pre> |
| >>> from implicit_ext import * |
| >>> x_value(X(42)) |
| 42 |
| >>> x_value(42) |
| 42 |
| >>> x = make_x(X(42)) |
| >>> x_value(x) |
| 42 |
| </pre> |
| |
| <p>Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
| 13 November, 2002 |
| <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
| </p> |
| |
| <p><i>© Copyright <a href= |
| "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> |
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